Demands for electronic equipment to increasingly provide higher-performance operation in smaller packages are ever present. Typically, such electronic equipment requires compact and highly efficient cooling systems to provide cooling air to power supplies, microprocessors, and related electronics that reside in the equipment. A typical cooling system involves moving air across one or more operating electronic components, such as printed circuit boards. The flow path layout, type of air moving device, and how well it is integrated into the system are each key elements in achieving desired cooling performance in a small package size.
Air movers of various type are available to select from in designing an electronics package cooling system. Such air mover types include axial fans and centrifugal blowers, which each exhibit advantages and disadvantages. Conventional systems, however, often employ fans and blowers that are not well matched to the system pressures, or do not move air efficiently within the space constraints, and therefore result in unacceptable noise and relatively large power consumption.
A particularly useful type of air mover is a double inlet centrifugal blower. Such blowers may be particularly well suited for restrictive flow systems that require a high volume of cooling air. Conventional implementations of centrifugal blowers typically employ a motor that is affixed in one of the two inlets, or inside the hub of the blower wheel with strut connections at one or both of the inlets. Neither conventional design is optimal, due to the motor occupying valuable aerodynamic space, which reduces the overall cooling efficiency of the blower, and creates unwanted noise. The hub motor approach also requires a hollow shaft and resultant manufacturing complexities associated with routing stator wires through a mounting shaft. An example conventional arrangement in which the motor is mounted in one of the two inlets of the centrifugal blower is that available from Fasco as model number B45267. An example of a double inlet centrifugal blower with a hub motor with a strut assembly for securing the motor inside of the hub is described in U.S. Pat. No. 2,776,088 to Wentling.
An alternate approach employs a mid-plane blower motor of the type described in U.S. Pat. No. 3,231,176 to Bowen. While the arrangement described in the Bowen '176 patent reduces the obstruction in the impeller volume, such design nevertheless employs struts for rotor support in the housing inlets. Such struts, as described above, inhibit aerodynamic efficiency.
It is therefore an object of the present invention to provide a double inlet centrifugal blower employing a strutless motor which minimizes aerodynamic interference and simplifies construction. In doing so, such a blower enhances operating efficiency to potentially reduce power consumption and noise output.